In recent years, developments have been actively conducted for a typical apparatus (such as a micromixer or a microreactor) to carry out mixing, emulsifying, a chemical reaction, an analysis, etc. of various solutions, etc. by utilizing the characteristics of microchannels. For example, a laminate-structured micromixer has been proposed in order to form a fine three dimensional channel structure or to increase microchannels thereby to improve the productivity (Patent Documents 1 and 2).
Further, in the case of a microreactor to carry out a chemical reaction in microchannels, in order to increase the productivity of the apparatus, it is required to elongate microchannels to prolong the retention time or to supply the raw material in a larger amount. In either case, the pressure to be exerted in the apparatus becomes high.
On the other hand, in the case of a micromixer to carry out mixing or emulsification in microchannels, in order to carry out the mixing or emulsification more quickly and uniformly, it is required to reduce the size of microchannels thereby to increase the linear velocity or to let the fluid flow through a complicatedly-shaped portion, and either case also leads to an increase of the operation pressure.
In an apparatus utilizing such microchannels, the uniformity in the reaction conditions such as the temperature, time, etc., the high proportion of contact area, and the laminar flow state, which are specific to microchannels, are utilized. Therefore, if the fluid moves in a lamination interface i.e. not in the microchannels in which the fluid is expected to flow, such means that the reaction cannot be carried out as designed. Especially, in the case of a micromixer to carry out uniform emulsification through micropores, it is required to reduce also the size of the micropores in order to obtain a more fine emulsion, and also in such an application, it is unavoidable that the operation pressure becomes high. In an apparatus designed for uniform emulsification, if a dispersion having transuded at a lamination interface, transudes into a channel for a mixture (emulsion), an emulsion having a particle size other than the desired particle size will be formed, whereby the desired product may not be obtained, and therefore, it is absolutely necessary to avoid such a phenomenon of transudation of the dispersion.
Further, in a micromixer or microreactor having a channel which is internally divided into a plurality of microchannels, if a fluid having a different viscosity, having transuded at a lamination interface, flows into a part of the channel, the flow tends to be nonuniform, whereby the desired product may not be obtained, and also from such a viewpoint, it is absolutely necessary to avoid such a phenomenon that the fluid having transuded at a lamination interface flows into an upstream channel than the microchannels.
In a laminate-type micromixer, a method has been proposed to carry out sealing by packing a soft material to prevent leakage into a lamination interface. Such leakage into a lamination interface is likely to occur as the internal pressure in operation is high, and therefore, it has been proposed to design the pressure to be lower so that no leakage will practically occur or to dispose microchannels by a design not to permit inclusion of a leaked fluid into the product channel even if leakage occurs.
A method has also been proposed to bond the laminated surfaces for integration, but with a view to cleaning the interior of the apparatus or change of the reagent to be used or the internal structure depending upon the particular purpose, a micromixer which can be designed and assembled depending upon the application is preferred, rather than bonding the laminated surfaces (Patent Document 3).
Further, in consideration of repeated use by cleaning many times, it is expected that the sealing may be deteriorated by scratches or deposited dusts between the laminated surfaces, and it is also desired to improve the reliability of such a portion.